This is a Phase II study designed to estimate the efficacy of weekly low-dose PEG-Intron in pediatric patients with CNS tumors, beginning 2-10 weeks after completion of radiation therapy. The endpoint of the trial is 2-year survival compared to historical controls who have received radiation alone. Patients undergo extensive imaging analysis. Accrual to this trial has been completed, patients are being followed for endpoint analyses, and biologic samples are being evaluated. All patients have tolerated the PEG-Intron therapy well, with no adverse events directly attributable to the study agent. Preliminary study results have been presented at the International Society of Pediatric Neuro-Oncology. We showed that patients receiving PEG-Intron have a median time to progression of 7 months compared to similar patients on recently completed consortia trials, who have a median time to progression of 4-5 months.